The invention relates to a strapping apparatus for strapping a tensioning strap around a packaged item, said apparatus including a frictional wheel which works against a support for tightening the named tensioning strap, wherein the frictional wheel is operatively connected to a drive and is liftable from the support by means of a pivot lever.
It is known, for example, to loop a plastics material or metal strap around a packaged item, a first, free end of the strap then forming a bottom strap at a connecting point and the other end of the strap, after forming the loop, forming a top strap at the connecting point. The top strap is then connected to the bottom strap at the connecting point, either, for example, in the case of metal straps as a result of clamping or in particular in the case of plastic material straps as a result of welding.
The overlapping top belt is then subsequently cut off close to the connection created in this manner such that the strap guided around the packaged item forms a ring.
So that said ring abuts closely against the packaged item, the strap has to be tightened tightly prior to forming the connection. To this end, it is known to guide the strap through the strapping apparatus between a frictional wheel and a support. The frictional wheel is then lowered onto the strap and made to rotate, as a result of which the strap is pulled through between the frictional wheel and the support.
At the end of the tightening operation, the addressed connection between the top and the bottom strap is then produced and the frictional wheel can then stop exerting a tensile force onto the strap.
As a result of the tensile force exerted by the frictional wheel onto the strap up to this point, in this case both the point of application of the force of the friction wheel on the strap and the drive elements connected upstream of the frictional wheel are under load. There is consequently the need to be able to bring about a load alleviation at this point in order to make it easier to handle the strapping apparatus then and also in the case of the next steps to be able to operate at little load and consequently in as wear-free a manner as possible.
In this case, for eliminating the load it is known to lift the frictional wheel up from the strap because, as a result, the load can be removed both from the connecting point between the frictional wheel and the strap and also from the drive train of the frictional wheel.
However, it has been shown that as a result of the forces or loads which act until the frictional wheel is lifted off and also have the effect of tensioning the drive train, the lowering or lifting mechanism for the frictional wheel can sometimes even jam, which restricts operating reliability.